1. Field of the Invention
The present invention relates to an ink jet recording head and a recording apparatus having such an ink jet recording head.
2. Related Background Art
(1) Almost all of ink jet recording apparatuses of this kind are generally connected to a word processor or a personal computer and are used as a color printer, a facsimile, a copying machine or the like. PA0 (2) On the other hand, since the ink jet recording method can provide a compact, light-weighted and cheap recording apparatus in which recording noise can be minimized and plain paper sheets can be used more easily than the other recording methods, many low cost printers utilize such ink jet recording method. Among the ink jet recording methods, a bubble jet recording method has recently been used since a large number of ink jet discharge ports can be arranged in an ink jet recording head with high density. PA0 (a) However, in the above-mentioned one-head type described in the above item (1), there arises the following problem. That is to say, since the resistive heat generating elements provided on the substrate are allotted to respective colors, the number of resistive heat generating elements associated with each color is reduced, thereby making high speed recording impossible. PA0 (b) In the arrangement in which the ink jet recording head is detachably mounted on the carriage and the ink tank is detachably connected to the ink jet recording head as described in the above item (2), it is necessary to design the ink jet recording head and the ink jet unit in consideration of the following precautions. That is to say, PA0 (A) In the ink jet recording head, the plurality of substrates having the resistive heat generating elements are urged against the top plate having the ink passages and the ink chambers by means of the elastic members. By manufacturing the top plate accurately and by forming the ink discharge ports with high accuracy by a laser beam by utilizing a reference surface formed on the top plate as a reference, color deviation can be prevented to improve recording quality and image quality, the number of parts can be reduced, an assembling time can be shortened, reliability and yield can be improved, and size can be reduced to provide a compact printer. Further, since the plurality of substrates having resistive heat generating elements are used, high speed recording can be achieved. In addition, since the groove (recess) having the depth greater than those of the ink passages is formed between the ink discharge port rows, the substrates can be closely contacted with the top plate effectively. PA0 (B) Since the ink discharge surface is not flush with the electrical connection surface and an ink supply surface, reliability can be improved, and, by arranging two ink discharge port rows at positions diametrically opposed to each other around a center between two ink discharge port rows, "cost-down" can be achieved because common parts can be used. Further, by connecting the ink supply portions to the head along the ink discharge direction, when the ink tank is mounted on and dismounted from the head, load acting on the head is distributed along the rows of the ink discharge ports uniformly, thereby preventing positional deviation of the head which would affect a bad influence upon the color recording.
Conventional ink jet recording heads used in color printers are generally grouped into three types, i.e., a one-head type in which an ink discharge portion of a single recording head is divided into colors (black, yellow, magenta and cyan). This type having an advantage that the head becomes cheaper although the number of nozzles per color is reduced, a multi-head type in which independent recording heads for respective colors are disposed side by side when printing is performed, this type having an advantage that the number of nozzles per color is increased, although the cost becomes higher, and a head unit type in which independent ink discharge portions for respective colors are incorporated into a single base.
In the one-head type, since the discharge ports for four colors can be formed in a single orifice plate, so long as manufacturing accuracy is ensured, assembling accuracy is not critical. Thus, positional accuracy of discharge ports for each color is improved to minimize print deviation, and the number of parts can be reduced to make the entire head more compact.
In the multi-head type, common parts can be used for respective heads, and the entire recording head can be easily manufactured because of simplicity of each head. However, since the plurality heads are arranged side by side, the entire recording head is made bulky and heavier.
In the head unit type, after positional deviation of ink droplets discharged from discharge ports of the orifice plates for respective color was measured and then such deviation was corrected, such orifice plate are incorporated into the base with high accuracy on the basis of the correction. Thus, the color deviation can be minimized. Further, replacement of heads can be easily performed because the heads are integrated as the unit. In addition, since a large number of discharge ports are associated with each color, high speed recording can be achieved.
In the conventional techniques, a wiring substrate including connection pads to be connected to the head(s) is secured to an ink container or a top plate. The top plate is secured to a substrate on which resistive heating elements are formed by adhesive or springs. When the springs are used, the top plate is rested on the substrate on which the resistive heating elements are formed and is secured to a base plate and the spring is mounted on the top plate.
In view of compactness and high speed recording which are required for an ink jet recording head of a color printer, the one-head type and the head unit type will be expected more and more from now.
In already known ink jet printers, ink supply is effected in the following two manners. In the first manner, the ink jet recording head is mounted on a carriage and an ink tank having large capacity (volume) is disposed at a predetermined position on a recording apparatus, and ink is supplied from the ink tank to the ink jet recording head through an ink tube.
In this arrangement, the running cost is very cheap. However, since it is required that a service life of the ink jet recording head itself is equal to or longer than a service life of the printer, the structure and material of the ink jet recording head must be devised, and, thus, the ink jet recording head itself tends to be expensive.
In the second manner, an ink tank and an ink jet recording head are integrated as an ink jet unit which is in turn detachably mounted on a carriage. In this arrangement, a long ink tube is not required, replacement of ink can easily be performed, and the entire apparatus can be made compact. However, at a time when the ink in the ink tank is used up, since both the ink tank and ink jet recording head must be replaced or exchanged, the running cost becomes expensive. Particularly, in such a case, since the ink jet recording head a service life of which has not yet been expired is also discarded, this is not preferred in view of ecology.
In order to eliminate the drawbacks associated with the above-mentioned two manners, there has been proposed an arrangement in which an ink jet recording head and an ink tank are detachably mounted on a carriage independently, as disclosed in Japanese Patent Laid-open No. 63-004953 (1988), for example. With this arrangement, since the ink jet recording head and the ink tank can be replaced independently, it is effective to reduce the running cost.
In the above-mentioned head unit type described in the above item (1), there arises the following problem. That is to say, when finer color image output is desired, since positional deviation between adhesion points (on a recording medium) of color ink droplets must be minimized, the orifice plates for respective colors must be assembled with high accuracy and the orifice plates must be secured to the base with high accuracy. Thus, the assembling time is increased and an expensive assembling machine must be used. Further, fundamentally, since several recording heads are arrange side by side, the size of the head unit is increased and the number of parts is also increased.
Further, since the wiring substrate including the connection pads is secured to an attachment member other than the ink tank or the top plate, the heads cannot be detached from the ink tank and thus the heads is obliged to be discarded together with the ink tank, and the number of parts is increased due to the presence of the attachment member. When the top plate is secured to the substrate having the resistive heat generating elements by using the springs, although the assembling operation can be facilitated, since the assembling is effected on the base plate, the number of parts is increased and the assembling time is also increased. Further, in order to assemble the substrate on which the plurality of resistive heat generating elements are formed on the base plate, the entire size is increased and the assembling time is also increased.
preventing reduction of electrical reliability due to adhesion of ink and/or paper powder;
improving accuracy of attachment of the ink jet recording head to the carriage and facilitating replacement of the ink tank;
improving positioning accuracy between the ink jet recording heads for effecting color recording; and
facilitating the manufacture of the ink jet recording head.